Fix ATIClampBug being true on NVIDIA/etc. cards

I assume the logic was inversed by accident.

I was puzzling over why S/T wrapping just was refusing to work for me, and I eventually realized that this was true, even though I'm on an NVIDIA card.

@DanyalZia, I assume that it is the ATI RADEON X / ATI MOBILITY RADEON X cards that have this bug?  Or are those the ATI cards that don't?  Either way, non-ATI cards should not have this set to true for sure...

-[Unknown]